1. Field of the Invention
The present invention relates to a fluid speed measuring probe for measuring the moving speed of a fluid and, more particularly, to a fluid speed measuring probe which utilizes a change in the resistance of a small piece of a single crystal of germanium with a change in temperature.
2. Description of the Prior Art
The applicant of the present invention discloses a fluid speed measuring probe composed of a sensor which is made of a small piece of a single crystal of germanium and coated with an electric insulating coating material in the form of a sphere so as to reduce the directivity of the sensor with respect to the direction of the flow of a fluid in Japanese Utility Model Laid-Open No. 47273/1988.
In this disclosure, by utilizing a small piece of a single crystal of geranium as a sensor, the problems in handling and the life time, which remain unsolved by a hot-wire anemometer utilizing a tungsten or platinum coil, are solved and by coating the sensor in the form of a sphere, the directivity of the sensor is reduced.
However, since an electric insulating synthetic resin is used as the coating material, the heat insulating property of the coating material makes it difficult to measure a minute change in the temperature of the probe surface which comes into contact with a fluid. In addition, it is impossible to completely eliminate the directivity of the sensor.